Color Filterless Display Device, Optical Element, and Manufacture

ABSTRACT

A method of forming an optical element for a color display device includes forming a lens shaped die, coating a low refractive index photo-setting resin on the lens shaped die, pasting the lens shaped die to a substrate, and irradiating the coated low refractive index photo-setting resin so as to set the low refractive index resin and form a low refractive index layer. The lens shaped die is removed from the low refractive index layer set on the substrate, a high refractive index photo-setting resin is coated on the low refractive index layer by use of a planarizing die, and the coated high refractive index photo-setting resin is irradiated so as to set the high refractive index resin and form a high refractive index layer. The planarizing die is then from the high refractive index layer set on the low refractive index layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/621,559, filed Jan. 9, 2007, which is a divisional application ofU.S. Pat. No. 7,164,454, which claims priority to Japanese PatentApplication JP2003295496, with Japanese filing date of Aug. 19, 2003,and all the benefits accruing therefrom under 35 U.S.C. §119, thecontents of which in its entirety are herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a color display device and the like,and more specifically, to a color display device capable of colordisplay without using color filters, and the like.

BACKGROUND OF THE INVENTION

A color liquid crystal display device widely used in recent years amongcolor display devices users has several hundred thousands to severalmillion pixels. Each pixel is composed of R (red), G (green) and B(blue) sub-pixels. In order to display the R, G and B for eachsub-pixel, R, G and B color filters are used in many cases, and a fullcolor image is obtained by combining displays of the sub-pixels usingthese color filters. In the case of using such color filters, two-thirdsof a light is absorbed by these color filters, and theoretically,approximately one-third of the light is only usable. In this connection,a color filterless display device performing color display without usingthe color filters is under study.

The following documents are considered herein:

-   [Patent Document 1] Gazette of Japanese Patent Laid-Open No.    2000-241812 (pp. 3 to 4, FIG. 1)-   [Patent Document 2] Gazette of Japanese Patent Laid-Open No. Hei 9    (1997)-311329 (p. 6, FIG. 1)-   [Patent Document 3] Specification of US Patent Application    Publication No. 2002-0075427

FIG. 13 is a view showing an example of a color filterless liquidcrystal display device, a configuration of a conventional colorfilterless and direct view liquid crystal display device using aspectral element (for example, refer to Patent Document 1). The deviceshown in FIG. 13 includes a light source 401 using, for example, a whitefluorescent tube, an incidence optical system 402, a reflection sheet403, a wedge-shaped light guide plate 404, a diffraction grating 405,and a cylindrical lens sheet 406 that is an optical element including aplurality of cylindrical lenses. Moreover, the device includespolarization films 407 sandwiching a liquid crystal cell 408there-between, a liquid crystal layer 410 sandwiched between glass 409and glass 409, all three of which compose the liquid crystal cell 408,and a diffusion/viewing angle correction film 411 made of a lightdiffusion film, a transmission diffraction grating film or the like.

In this color filterless and direct view liquid crystal display device,a white light incident from the light source 401 is guided by thewedge-shaped light guide plate 404, and a planer light is emitted in thevicinity of a desired incident angle. The white light incident from thewedge-shaped light guide plate 404 is separated by an optical element(spectral element) such as the diffraction grating 405 (and an opticalhologram). By this light separation, three-color diffracted light of theR, G and B is emitted at angles where the blue (B) light and the red (R)light are arrayed to be substantially symmetric bilaterally with respectto the green (G) light diffracted to a frontal direction as a center.The diffracted light of the respective colors is made incident onto thecylindrical lens sheet 406. Here, one pixel among the display pixels iscomposed of three sub-pixels of the R, G and B. With regard to the lightincident onto the cylindrical lens sheet 406, for the liquid crystalcell 408, the R light is made incident onto a sub-pixel for the R, the Glight is made incident onto a sub-pixel for the G, and the B light ismade incident onto a sub-pixel for the B. Then, transmission and cutoffof the light is controlled for each sub-pixel. On a surface of theliquid crystal cell 408, an emitted light from the liquid crystal cellhas emission angles different depending on the wavelengths due todiffraction angles depending on wavelengths of the colors. Accordingly,in order to widen a viewing angle of the liquid crystal cell 408, thelight diffusion/viewing angle correction by the diffusion/viewing anglecorrection film 411 is performed. Note that, also in other color displaydevices such as a color filterless liquid crystal projection device,lights of the respective colors, which is made incident onto a liquidcrystal cell in a state of being emitted from a white light source,separated by a dichroic mirror, a diffraction grating or the like, andcondensed by a lens element, has different incident angle for each ofthe respective colors of the R, G and B.

However, in the conventional color filterless and direct view liquidcrystal display device as shown in FIG. 13, a problem remains in termsof an effect of such a viewing angle correcting function member. By useonly of the usual diffusion/viewing angle correction film 411, theemission angles from the liquid crystal cell, which depend on thewavelengths, are maintained even after the emitted light transmitsthrough the diffusion/viewing angle correction film 411. In order toequalize color reproductivity and color balance and to widely secure theviewing angle, it is desired to add a far more improvement. Accordingly,it is also conceivable to separately use a transmission diffractiongrating film as the viewing angle correcting function member. However,film design to control diffraction efficiencies different depending onthe wavelengths and to correct intensity of the incident light of everywavelength with high accuracy into a distribution of the equalizedviewing angles is accompanied with difficulty. Moreover, a significantlowering of a peak value of luminance to the frontal direction cannot beavoided. For example, a relative value of luminance of the emitted lighton the front in comparison to the incident light onto the correctionfilm is undesirably lowered to 30 to 40%. Furthermore, because of acombination of the materials having the different refractive indices,fabrication itself of a film into a shape combining high diffractionefficiency and a smooth surface is difficult. For example, in adiffraction grating having a triangular cross-sectional shape and usingmaterials with refractive indices of 1.42 and 1.57, arithmetically, sucha shape incapable of being fabricated, as in which an inner inclinationangle between the two layers is 70 to 80 degrees, is needed.

FIGS. 14( a) and 14(b) are graphs showing distributions of the emittedlight in the color filterless and direct view liquid crystal displaydevice. FIG. 14( a) shows a distribution of the emitted light in thecase where the viewing angle correcting diffraction grating is notprovided, and FIG. 14( b) shows a distribution of the emitted light inthe case where the transmission diffraction grating film is concurrentlyused as the viewing angle correcting function member. In each of thegraphs, an abscissa axis represents an output angle, an ordinate axisrepresents transmissivity, and the distributions of the emitted light ofthe respective colors R, G and B are shown. In comparison with the casewhere the viewing angle correcting diffraction grating is not provided,which is shown in FIG. 14( a), in the case where the viewing anglecorrecting diffraction grating is provided, which is shown in FIG. 14(b), each center of the emitted light R, G and B comes close to a frontaldirection of a panel. However, deviations among the lights of therespective colors are not removed, and the viewing angle correctingfunction member does not necessarily have a sufficient viewing anglecorrecting function.

The following should be noted. It has been measured that the colorreproductivity (an area of a region displayable by the color displaydevice in a chromaticity diagram) in the frontal direction in the caseof concurrently using the transmission diffraction grating film as theviewing angle correcting function member becomes, for example,approximately 38% at the NTSC rate, which remains equal to or less than42% at the NTSC rate of a direct view liquid crystal display deviceadded with an existing 13.3-inch color filter. Moreover, if a conditionof a viewing angle at which chromaticity is regarded as uniform isdefined such that an error between a subject emitted component and anemitted component to the frontal direction falls within a range equal toor less than 0.02 in both chromaticity coordinates x and y, it has beenconfirmed that an emission angle range meeting the condition remainswithin, for example, a narrow range from −5 to +7 degrees. Because ofthese defects, with the transmission diffraction film, it is difficultto accomplish a sufficient viewing angle correcting function inluminance/chromaticity. Accordingly, a new viewing angle correctingmethod for improving viewing angle performance is required. Moreover,with regard to the luminance, from an observation of the inventors ofthe present invention, it is grasped that, for example, a luminancevalue on the front side before adding the transmission diffractiongrating film is approximately 217 cd/m.sup.2, and a luminance value onthe front side thereafter is approximately 85 cd/m.sup.2, both of whichare results of attenuation to 40% or less in such an insufficient stateof the color reproductivity. Therefore, an improvement for enhancing theluminance is also necessary.

Here, as the conventional viewing angle correcting function member, astructure has been proposed, in which lens-shaped or prism-shapedconcave portions are processed and formed in a size corresponding toopening portions of the respective sub-pixels of the R, G and B on ablack matrix-side surface of an emission-side glass substrate of theliquid crystal cell, and polymer having a refractive index higher thanthat of the glass substrate is injected into the concave portions, thusplanarizing the surface (for example, refer to Patent Document 2).Moreover, the inventors of the present invention have proposed atechnology in which a simple prism structure or a Fresnel-typemicroprism structure is introduced to the color filterless and directview liquid crystal display device (refer to Patent Document 3).

In the above-described technology described in Patent Document 2, aviewing angle correction effect to the frontal direction by refractioncan be expected to some extent. However, a cycle of a lens/prismstructure is designed while corresponding to an amount of one pixel,that is, of three sub-pixels, and accordingly, in terms of parallelingthe emitted light by restricting an angle expansion phenomenon itselfthereof, which is caused by the condensing function element between abacklight and the liquid crystal cell, a diffusion suppression effectcannot be expected. Particularly, though an R light and a B light, whichare made incident onto ends of a lens portion (denoted by a referencenumeral 30 in FIG. 1), are illustrated as if both of the light becameparallel to each other when being emitted in the content illustrated inFIG. 1 of Patent Document 2, the incident light is actually emitted to adiffusing direction on such illustrated ends of the lens portion.Therefore, a sufficient angle correction cannot be performed.

Moreover, in the technology proposed in Patent Document 3, far moreproblems to be solved for practical use are left. For example, a lighttravels from a low refractive layer to a high refractive layer in thetechnology proposed in Patent Document 3, and in order to perform theangle correction, it is necessary to improve a prism structure describedin Patent Document 3. Particularly, it is necessary to study more inorder to make it difficult to produce “shading” for the incident light.

SUMMARY OF THE INVENTION

Therefore, the present invention provides solutions to the technicalproblems described above. It is an aspect of the present invention torealize a display image, which has, for example, wide-range colorreproductivity and a wide viewing angle and is clear without blur, byperforming an angle correction for each sub-pixel to a desired directionin response to an incident angle of an incident light.

It is another aspect of the present invention to make substantiallyparallel emitted light of each sub-pixel to the other by the anglecorrection.

It is still another aspect of the present invention to improve the colorreproductivity by performing a design corresponding to a spectralstructure of wavelengths included in a light source.

On the basis of such aspects, in a color display device to which thepresent invention is applied, first, a light irradiated from, forexample, a white light source is separated into lights of a plurality ofwavelength regions by wavelength separation means such as, for example,a diffraction grating. Then, by condensing means for receiving the lightseparated by this wavelength separating means and formed of, forexample, a lens and the like, the lights of predetermined wavelengthregions is condensed while corresponding to predetermined sub-pixels(for example, sub-pixels of red (R), green (G) and blue (B) constitutingone pixel). With regard to the condensed light, due to diffractionangles depending on the wavelengths, angle distributions of the emittedlight from the respective sub-pixels do not coincide with one another,for example, in the respective colors of the red (R), green (G) and blue(B). Accordingly, a configuration is adopted such that the light of therespective sub-pixels, which is condensed by the condensing means forthe respective sub-pixels, is emitted by the angle correcting meanswhile giving thereto a distribution of emission angles approximatelysymmetric and equivalent with respect to a frontal direction as acenter.

A color display device to which the present invention is appliedcomprises: a light source; wavelength separation means for separating alight irradiated from the light source into lights of a plurality ofwavelength regions; condensing means for receiving the light separatedby this wavelength separation means and condensing lights ofpredetermined wavelength regions while corresponding to predeterminedsub-pixels; and angle correcting means for substantially paralleling thelight of each sub-pixel toward a predetermined direction, the lightbeing condensed by the condensing means for each of the sub-pixels.

A color display device to which the present invention is applied ischaracterized in that, in the structure portion for correcting an angleof the light of each sub-pixel, the light being condensed by thecondensing element, for each of the sub-pixels corresponding to the red(R), the green (G) and the blue (B), a high refractive index layer isformed on a side onto which the light is made incident from thecondensing element, a low refractive index layer is formed on anemitting side from which the light is emitted, and a predeterminedinterface is formed by these layers, and the interface is characterizedby being substantially symmetric bilaterally and tilted to approximately45 degrees for the sub-pixels corresponding to the red (R) and the blue(B), and tilted to approximately 14 degrees for the sub-pixelcorresponding to the green (G).

The present invention also provides an optical element for correctingemission angles of a light incident at different angles depending onwavelengths, comprising: a high refractive index layer formed of firstpolymer and provided on a light incident side; and a low refractiveindex layer formed of second polymer having a refractive index lowerthan the first polymer and provided in contact with the high refractiveindex layer on a light emitting side, characterized in that the highrefractive index layer and the low refractive index layer have differentshapes for each of sub-pixels corresponding to respective colors of red(R), green (G) and blue (B). Here, these high refractive index layer andlow refractive index layer can be characterized by forming a prismstructure, and characterized in that angles of prisms differ for each ofthe sub-pixels. Moreover, these high refractive index layer and lowrefractive index layer can be characterized by forming a lens structurefor each of the sub-pixels.

Furthermore, the present invention provides a method of manufacturing acolor display device made by forming an optical element on a substrate.A manufacturing method comprises the steps of: coating low refractiveindex photo-setting resin on a die on which a predetermined shape isformed in response to sub-pixels corresponding to respective colors;pasting these die and substrate together and irradiating a light on thecoated low refractive index photo-setting resin for setting; afterpeeling off the die, coating high refractive index photo-setting resinon the set low refractive index resin by use of a planarizing die; anirradiating light on the coated high refractive index photo-settingresin for setting; and peeling off the planarizing die from thesubstrate.

According to the present invention, for example, in the color displaydevice which does not use the color filter but utilizes the spectralelement, color display having wide color reproductivity, a wide viewingangle and clearness and restricting blur can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages there of, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view showing a configuration of a color filterless liquidcrystal display device (color filterless and direct view liquid crystaldisplay device) to which this embodiment is applied;

FIG. 2 is a view for explaining a simple microprism structure built in aliquid crystal cell of this embodiment;

FIG. 3 is a view for explaining a linear Fresnel-type microprismstructure built in the liquid crystal cell of this embodiment, as astructure replacing that in FIG. 2;

FIG. 4 is a view for explaining optimization of a relationship betweenan incident light (emitted light) and two basic angles of a slope and anopposite slope;

FIG. 5 is a graph showing a relationship between the basic angle of theopposite slope and occurrence rates of two kinds of shadings, which areshading A and shading B;

FIGS. 6( a) and 6(b) are graphs showing results obtained by actuallymeasuring differences in a distribution of viewing angles of spectrumintensities of lights of respective colors of R, G and B (whendisplaying a white color) before and after forming a microprism in theliquid crystal cell;

FIGS. 7( a) and 7(b) are graphs, each showing a relationship between aposition of a black matrix and a light source spectrum;

FIG. 8 is a view showing an example of mounting a microlens on theliquid crystal cell;

FIG. 9 is a view showing an example of mounting a microlens on theliquid crystal cell;

FIG. 10 is a view showing an example of mounting a Fresnel-typemicrolens shape on the liquid crystal cell;

FIG. 11 is a view showing an example of mounting a Fresnel-typemicrolens shape on the liquid crystal cell;

FIG. 12 is a flowchart showing a process of a method of manufacturingthe microprism/microlens;

FIG. 13 is a view showing, as an example of the color filterless liquidcrystal display device, a configuration of a conventional colorfilterless and direct view liquid crystal display device using aspectral element; and

FIGS. 14( a) and 14(b) are graphs showing distributions of an emittedlight in the color filterless and direct view liquid crystal displaydevice.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a display image, which has, for example,wide-range color reproductivity and a wide viewing angle and is clearwithout blur, by performing an angle correction for each sub-pixel to adesired direction in response to an incident angle of an incident light.The present invention also makes substantially parallel emitted light ofeach sub-pixel to the other by the angle correction. The presentinvention also improves the color reproductivity by performing a designcorresponding to a spectral structure of wavelengths included in a lightsource.

In a color display device to which the present invention is applied,first, a light irradiated from, for example, a white light source isseparated into lights of a plurality of wavelength regions by wavelengthseparation means such as, for example, a diffraction grating. Then, bycondensing means for receiving the light separated by this wavelengthseparating means and formed of, for example, a lens and the like, thelights of predetermined wavelength regions is condensed whilecorresponding to predetermined sub-pixels (for example, sub-pixels ofred (R), green (G) and blue (B) constituting one pixel). With regard tothe condensed light, due to diffraction angles depending on thewavelengths, angle distributions of the emitted light from therespective sub-pixels do not coincide with one another, for example, inthe respective colors of the red (R), green (G) and blue (B).Accordingly, a configuration is adopted such that the light of therespective sub-pixels, which is condensed by the condensing means forthe respective sub-pixels, is emitted by the angle correcting meanswhile giving thereto a distribution of emission angles approximatelysymmetric and equivalent with respect to a frontal direction as acenter.

Here, this angle correcting means can be characterized by beingconstituted of an optical structure in which a light incident side ismade of a high refractive index layer, a light emitting side is made ofa low refractive index layer, and a shape is made to differ for each ofthe sub-pixels. More specifically, this angle correcting means ischaracterized by having a prism structure or a Fresnel-type microprismstructure in which an angle of an interface between the high refractiveindex layer and the low refractive index layer is different for each ofthe sub-pixels. Furthermore, if a configuration is adopted so as toinclude cutoff means for cutting off a light of a wavelength other thanthe light separated into each of the sub-pixels, in which its shape isdetermined to meet that wavelength, it is preferable in that, forexample, an orange wavelength component and a cyan wavelength component,which hinder the color reproductivity, can be sufficiently cut out.

An example of a color display device to which the present invention isapplied comprises: a light source; wavelength separation means forseparating a light irradiated from the light source into lights of aplurality of wavelength regions; condensing means for receiving thelight separated by this wavelength separation means and condensinglights of predetermined wavelength regions while corresponding topredetermined sub-pixels; and angle correcting means for substantiallyparalleling the light of each sub-pixel toward a predetermineddirection, the light being condensed by the condensing means for each ofthe sub-pixels. More specifically, this angle correcting means can becharacterized by forming, by a high refractive index layer and a lowrefractive index layer, a microlens structure in which a light incidentside is made of the high refractive index layer, a light emitting sideis made of the low refractive index layer, and tilt angles are differentfor each of the sub-pixels.

Moreover, when being grasped from another viewpoint, the presentinvention is a color display device for expressing one pixel by threesub-pixels of red (R), green (G) and blue (B), comprising: a lightsource; a spectral element for separating a light irradiated from thislight source into lights of a plurality of wavelength regions; acondensing element for receiving the light separated by this spectralelement and condensing the light while corresponding to each of thesub-pixels of the red (R), green (G) and blue (B); and a structureportion for correcting an angle of the light condensed by the condensingelement for each of the sub-pixels corresponding to the red (R), thegreen (G) and the blue (B), characterized in that this structure portionforms, by a high refractive index layer and a low refractive indexlayer, a Fresnel-type microprism structure in which a side onto whichthe light is made incident from the condensing element is made of thehigh refractive index layer, an emitting side from which the light isemitted is made of the low refractive index layer.

Here, the Fresnel-type microprism structure in this structure portioncan be characterized by having shapes different for each of thesub-pixels. More specifically, if this Fresnel-type microprism structurein the structure portion is characterized by forming slopes having basicangles at approximately 45 degrees for the sub-pixels of the red (R) andblue (B) and a basic angle at approximately 14 degrees for the sub-pixelof the green (G), it is preferable in that the viewing anglecharacteristics and the color reproductivity in the frontal directioncan cover a wide range. Moreover, if, the Fresnel-type microprismstructure in this structure portion is characterized in that a basicangle of an opposite slope of the microprism structure is 70 degrees ormore to less than 90 degrees, this is excellent also in that “shading”caused by a light colliding with this opposite slope adjacent to theslope can be restricted more.

An example of a color display device to which the present invention isapplied is characterized in that, in the structure portion forcorrecting an angle of the light of each sub-pixel, the light beingcondensed by the condensing element, for each of the sub-pixelscorresponding to the red (R), the green (G) and the blue (B), a highrefractive index layer is formed on a side onto which the light is madeincident from the condensing element, a low refractive index layer isformed on an emitting side from which the light is emitted, and apredetermined interface is formed by these layers, and the interface ischaracterized by being substantially symmetric bilaterally and tilted toapproximately 45 degrees for the sub-pixels corresponding to the red (R)and the blue (B), and tilted to approximately 14 degrees for thesub-pixel corresponding to the green (G).

Furthermore, when being grasped from another viewpoint, in a structureportion for correcting an angle of the light of each sub-pixel, thelight being condensed by the condensing element, for each of thesub-pixels corresponding to the red (R), the green (G) and the blue (B),a color display device to which the present invention is applied makes ahigh refractive index layer on a side onto which the light is madeincident from the condensing element, makes a low refractive index layeron an emitting side from which the light is emitted, and forms apredetermined interface by these layers, and the interface forms a lensstructure for each of the sub-pixels. Here, if this lens structure ischaracterized in that a tilt angle is set for each of the sub-pixels, itis preferable in that a substantially parallel light mainly directed tothe frontal direction can be obtained in each sub-pixel. Moreover, ifthe interface of this structure portion is characterized by including aFresnel-type microlens structure formed of shapes different for each ofthe sub-pixels, it is made possible to thin thickness of the structureportion.

Moreover, the present invention provides an optical element forcorrecting emission angles of a light incident at different anglesdepending on wavelengths, comprising: a high refractive index layerformed of first polymer and provided on a light incident side; and a lowrefractive index layer formed of second polymer having a refractiveindex lower than the first polymer and provided in contact with the highrefractive index layer on a light emitting side, characterized in thatthe high refractive index layer and the low refractive index layer havedifferent shapes for each of sub-pixels corresponding to respectivecolors of red (R), green (G) and blue (B). Here, these high refractiveindex layer and low refractive index layer can be characterized byforming a prism structure, and characterized in that angles of prismsdiffer for each of the sub-pixels. Moreover, these high refractive indexlayer and low refractive index layer can be characterized by forming alens structure for each of the sub-pixels.

Furthermore, the present invention can be grasped as a method ofmanufacturing a color display device made by forming an optical elementon a substrate. This manufacturing method comprises the steps of:coating low refractive index photo-setting resin on a die on which apredetermined shape is formed in response to sub-pixels corresponding torespective colors; pasting these die and substrate together andirradiating a light on the coated low refractive index photo-settingresin for setting; after peeling off the die, coating high refractiveindex photo-setting resin on the set low refractive index resin by useof a planarizing die; an irradiating light on the coated high refractiveindex photo-setting resin for setting; and peeling off the planarizingdie from the substrate.

Thus, in accordance with the present invention, a color display devicewhich does not use a color filter but utilizes a spectral element, colordisplay having wide color reproductivity, a wide viewing angle andclearness and restricting blur can be realized.

Embodiments of the present invention will be described below in detailwith reference to the accompanying drawings.

Embodiment 1

FIG. 1 is a view showing a configuration of a color filterless liquidcrystal display device (color filterless and direct view liquid crystaldisplay device) to which this embodiment is applied. This colorfilterless liquid crystal display device includes a light source 11using, for example, a straight white fluorescent tube, an incidenceoptical system 12 a guiding light from the light source 11, a lightguide plate 13 having, for example, a wedge shape, a reflection sheet14, and a diffraction grating 15 as a spectral element separating theincident white light into a red (R) light, a green (G) light and a blue(B) light. Moreover, this liquid crystal display includes a liquidcrystal cell 20, a cylindrical lens array 16 as an optical element(condensing element) provided with a plurality of cylindrical lenses orthe like, polarization films 17, and a diffusion film 18. The liquidcrystal cell 20 includes a liquid crystal layer inserted between twoglass substrates as will be described later. Moreover, between the twoglass substrates, the liquid crystal cell 20 includes a prism structureportion (to be described later) as a characteristic configuration inthis embodiment. Note that, in this embodiment, a film for correcting aviewing angle, which has been conventionally provided in a portion ofthe diffusion film 18, is not needed.

The light irradiated from the light source 11 is made incident onto thelight guide plate 13 through the incidence optical system 12. The lightincident onto the light guide plate 13 makes an angle thereof graduallysteep while repeatedly reflecting on a lower surface (reflection sheet14-side surface) and upper surface (liquid crystal cell 20-side surface)of the light guide plate 13. When a direction of the light exceeds acritical angle on the upper surface, the light is emitted from thisupper surface. The emitted light is separated into the R, G and B lightin the diffraction grating 15 or an optical element (spectral element)such as, for example, an optical hologram, which functions as one ofwavelength separation means. The separated light is polarized by thepolarization film 17 and made incident onto the cylindrical lens array16. In the cylindrical lens array 16, the plurality of cylindricallenses are provided, and for example, one cylindrical lens correspondsto one pixel. One pixel is composed of three sub-pixels that are for theR, G and B. For the separated and polarized light, transmission orcutoff is controlled for each sub-pixel by the liquid crystal cell 20.The light for each sub-pixel, which has transmitted through the liquidcrystal cell 20, passes through the polarization film 17 and is diffusedby the diffusion film 18.

In such a color filterless liquid crystal display device as shown inFIG. 1, accompanied with position conversion in response to angles bythe cylindrical lens array 16 that is a lens element, the emitted lightfrom a backlight system, which has emission angles different dependingon the wavelengths, is made incident onto specific sub-pixels among therespective pixels in the liquid crystal cell 20 in a condensed state. Inthis case, in order to sufficiently enhance viewing anglecharacteristics in a distribution of the emitted light of the liquidcrystal cell 20 in the direct view and color filterless liquid crystaldisplay device, it is necessary to solve asymmetry inluminance/chromaticity in the distribution of the emitted light and ashortage of the viewing angle correcting function itself, both of whichhave been regarded as problems in the conventional viewing anglecorrection film as shown in FIG. 14( b). In order to impart, to suchincident components onto the liquid crystal cell 20, a distribution ofemission angles from the liquid crystal cell, which are symmetric andequivalent with respect to the frontal direction as a center, in thisembodiment, an optical element having a microprism structure as below isintroduced such that desired angle corrections can be performed for thewhole of the incident light. The microprism structure is: a simplemicroprism structure (in FIG. 2 and the like to be referred to later)built in the liquid crystal cell; or a linear Fresnel-type microprismstructure (in FIG. 3 and the like to be referred to later), each ofwhich changes a shape thereof for each sub-pixel corresponding to eachcolor of the R, G and B. Thus, design for optimization is performed.

Here, a method is also conceivable, in which a viewing angle correctingfunction member of a similar shape to that of the above-describedoptical element is realized by an independent prism array sheet andpasted on the concerned liquid crystal cell 20. However, in such a case,due to optical design in which an image is formed in the liquid crystalcell 20, a parallax occurs in the emitted light after the viewing anglecorrection. Moreover, in the case of pasting such an optical film on theglass substrate 22, it is proven that alignment accuracy thereof withthe liquid crystal cell 20 greatly deviates from a tolerance due to amechanical stress, and for example, remains as low as ±70 μm or more per200 mm. Accordingly, in this embodiment, the microprism structure of theliquid crystal cell built-in type is adopted.

Note that the configuration of the liquid crystal cell 20 in the colorfilterless liquid crystal display device as shown in FIG. 1 can also beapplied to a liquid crystal projection display device projecting aprojection image on a screen.

FIG. 2 is a view for explaining the simple microprism structure built inthe liquid crystal cell 20 of this embodiment. The liquid crystal cell20 shown in FIG. 2 includes a liquid crystal layer 23 and a prismstructure portion 30 between a bottom-side glass substrate 21 and atop-side glass substrate 22. In the liquid crystal layer 23, TFTs 24 areformed, and on the top-side glass substrate 22, a black matrix (BM) 25partitioning the respective sub-pixels of the R, G and B is provided. Inthe prism structure portion 30, a high refractive index layer 31 havinga refractive index of, for example, 1.55 is provided on a light incidentside (bottom side), and a low refractive index layer 32 having arefractive index of, for example, 1.408 is provided on a light emittingside (top side). For this high refractive index layer 31, for example,photo-setting acrylic resin is used as first polymer, and for the lowrefractive index layer 32, for example, fluoridated photo-settingacrylic resin can be used as second polymer.

In designing such a simple microprism structure, the inventors of thepresent invention determined a shape of the prism structure portion 30,which adjusts, in the prism structure portion built in the cell, viewingangle dependencies mutually different and inherent in the light of therespective colors of R, G and B when being made incident onto the liquidcrystal cell 20, and maximizes the viewing angle characteristics and thecolor reproductivity in the frontal direction. Mainly, the inventorsdetermined the optimum inclination angle and basic angle of the prism.In designing the prism structure portion 30, an actual value of aviewing angle distribution of each wavelength component emitted from thespectral element (diffraction grating 15) with regard to an emissionintensity from the backlight is utilized. Then, by a calculation methodof performing ray tracing for a light intensity from the cylindricallens array 16 to the liquid crystal cell 20 building the prism structureportion 30 therein by use of three values of relative positioncoordinates thereof to a wavelength, an angle and a pixel as parameters,high accuracy design calculation coinciding quantitatively with theactual value was performed. By this design calculation, there wasobtained a result to the effect that the viewing angle characteristicsand the color reproductivity in the frontal direction cover the widestrange when an inclination angle of an interface between the highrefractive index layer 31 and the low refractive index layer 32 for eachsub-pixel of the red (R) and blue (B) is approximately 45 degrees and aninclination angle of an interface between the high refractive indexlayer 31 and the low refractive index layer 32 for the sub-pixel of thegreen (G) is approximately 14 degrees. In the liquid crystal cell 20shown in FIG. 2, in order to set, at 45 degrees, the inclination angleof the interface between the high refractive index layer 31 and the lowrefractive index layer 32, through which the incident light of the R andB transmits while being refracted, as a thickness of the prism structureportion 30, approximately 90 to 100 μm is necessary for 88 μm of a widthof one sub-pixel. Note that a thickness of each of the glass substrates21 and 22 is approximately 700 μm.

FIG. 3 is a view for explaining the linear Fresnel-type microprismstructure built in the liquid crystal cell 20 of this embodiment, as astructure replacing that in FIG. 2. A prism structure portion 40 shownin FIG. 3 is different from the structure shown in FIG. 2 in that amicroprism structure formed of a high refractive index layer 41 and alow refractive index layer 42 is formed of a fine Fresnel prism havingshapes of small convexes and concaves on surfaces thereof. By adoptingthis fine Fresnel type, a thickness of the prism structure portion 40shown in FIG. 3 can be thinned to approximately 10 μm. Moreover, theprism structure portion 40 can be made as a thin flat layer, and it isalso made possible to reduce unevenness of a cell gap and to maintainevenness thereof. In the example shown in FIG. 3, two kinds of polymers,which have a cycle of the Fresnel prism in the prism structure portion40 at 88 μm, and individually have refractive indices of 1.55 (for thehigh refractive index layer 41) and 1.408 (for the low refractive indexlayer 42), are combined, and a Fresnel prism having a cyclic structureof a triangular cross-sectional shape is formed. As shown in an enlargedview shown in FIG. 3, with regard to the shape of each triangle in thisFresnel prism, a basic angle of a slope is 45 degrees and a basic angleof a slope opposite thereto is 80 degrees in the sub-pixel portion ofthe R. The sub-pixel portion of the B also has a triangular shapesymmetric bilaterally to that of the R, and is formed at the same basicangles. Meanwhile, the sub-pixel portion of the G is formed such that abasic angle of a slope is 14 degrees and a basic angle of a slopeopposite thereto is 80 degrees. With such formation, the viewing anglecharacteristics can be enhanced, and the color reproductivity in thefrontal direction can cover a wide range.

Here, in this embodiment, the incident light of each color travels fromthe high refractive index layers 31 and 41 to the low refractive indexlayers 32 to 42. On the other hand, in Patent Document 3 described inthe background art, this relation is inverted, and the incident lighttravels from a low refractive index layer to a high refractive indexlayer. The slopes of the Fresnel prism shown in the enlarged view ofFIG. 3 have an object to perform angle correction of the incident lightby refraction and transmission thereof. However, when the incident lighttravels from the low refractive index layer to the high refractive indexlayer as in the background art, the incident light is expanded, and theangle correction thereof comes to be impossible. Moreover, even if anorientation of the slope of the Fresnel prism is adjusted, the other ofthe pair of slopes, which is the opposite slope, will be located to acenter side of each pixel and receive the incident light more. This willmake shading prone to occur in the incident light, and will result inthat components reflecting and diffusing in directions other than thedirection for the angle correction are increased. As such a result thatthe shading occurs in the incident light on the opposite slope, a smallpeak becoming a hindrance of the angle correction appears in an emissiondistribution and deteriorates the color reproductivity. Therefore, as inthis embodiment, it is effective to adopt the structure in which theincident light travels from the high refractive index layers 31 and 41to the low refractive index layers 32 and 42.

Next, two basic angles of the slope and the opposite slope will bedescribed. FIG. 4 is a view for explaining optimization of arelationship between the incident light (emitted light) and the twobasic angles of the slope and the opposite slope. Among the incidentlight onto the Fresnel-type microprism structure, incident light ofExample 1, which is shown in FIG. 4, is refracted on the slope formed ofthe high refractive index layer 41 and the low refractive index layer42, and becomes an incident light for which a right correction of theangle has been performed. However, a part of the incident light does notcollide with the slope formed originally for correcting the angle, butfirst collides with the opposite slope to cause the shading, and isreflected/diffused to the direction other than the direction for theangle correction. A ratio of this reflected/diffused light is increasedas the basic angle of the opposite slope becomes smaller and aninclination thereof becomes gentler. In FIG. 4, a state is shown, wherean incident light of Example 3 is reflected/diffused on the oppositeslope and becomes shading A. Meanwhile, when the basic angle of theopposite slope in each prism in the Fresnel-type microprism structure isset at, for example, 90 degrees or more, a part of a light componentthat has been refracted on and transmitted through the slope for use inthe angle correction then collides with the opposite slope adjacentthereto, the shading becomes prone to occur, and thereflection/diffusion to the direction other than the direction for theangle correction become prone to occur. In FIG. 4, a state is shown,where an incident light of Example 2, which is a part of the lightcomponent that has been refracted on and transmitted through the slope,is reflected/diffused by the opposite slope and causes shadings B. Anoccurrence rate of these shadings B is increased as the basic angle ofthe opposite slope as shown in the enlarged view of FIG. 3 becomeslarger and steeper. Moreover, also from a viewpoint of manufacturing thestructure, difficulty fabricating a metal die and a copy of thestructure is increased as the basic angle of the opposite slope becomessteeper.

FIG. 5 is a graph showing a relationship between the basic angle of theopposite slope and the occurrence rates of the two kinds of shadings,which are the shading A and the shading B. An abscissa axis representsthe basic angle (deg) of the opposite slope of the Fresnel prism, and anordinate axis represents a ratio of an emitted light without shading.The shading A is reduced as the basic angle (inclination angle) of theopposite slope becomes larger. Meanwhile, the shading B is reduced asthe basic angle of the opposite slope becomes smaller. Under conditionsin this embodiment, an intersection of the occurrence rates at whichthese two kinds of shadings occur is within a range from 70 degrees ormore to less than 90 degrees of the basic angle of the opposite slope,and preferably, within a range from 75 degrees to 80 degrees. In theprism structure portion 40 in this embodiment, for the purpose ofrestricting the occurrence rate of the shading A that reflects/diffusesthe emitted light at a larger angle and asymmetrizes the distributionthereof, design is made such that the basic angle of the opposite slopeis set somewhat large and the optimum value thereof becomes 80 degrees(less than 90 degrees).

In such a way, in this embodiment, the two-layer flat structure of thelinear Fresnel-type microprism shape, which is extremely thinned, can beformed easily in the liquid crystal cell 20 as shown in FIG. 3.Accordingly, the structure does not hinder the evenness of the cell gap,and it is possible to incorporate the structure in an additional processin a manufacturing process of the conventional liquid crystal cell 20.Moreover, it is possible to make the individual prism shape in thesub-pixel into a variable structure, and accordingly, a local fineadjustment to meet the optimum optical design condition is also madepossible.

Here, a white-color display was performed by the color filterless anddirect view liquid crystal display device employing the microprism builtin the liquid crystal cell, and the emitted lights from the respectivesub-pixels was observed by microscope. Then, it was able to be confirmedthat color emissions in response to the respective sub-pixels of thered, green and blue were realized in the frontal direction with highpositioning accuracy. With regard to frontal luminance in a prototype,an actual value is 200 cd/m.sup.2 (162 cd/m.sup.2 without themicroprism) while a design value is 204 cd/m.sup.2. This is a luminancevalue more than twice luminance when using a viewing angle correctingdiffraction grating film using a similar backlight. By the microprism,the angle correction is performed for the light of every wavelength,which is included in the white light source, to the vicinity of thefrontal direction, and accordingly, an enhancement of the frontalluminance is confirmed as compared with the case without using theprism.

FIGS. 6( a) and 6(b) are graphs showing results obtained by actuallymeasuring differences in the distribution of the viewing angles ofspectrum intensities of the light of the respective colors of R, G and B(when displaying the white color) before and after forming themicroprism in the liquid crystal cell. FIG. 6( a) shows actual valuesbefore forming the microprism, and FIG. 6( b) shows actual values afterforming the microprism. Abscissa axes represent output angles, andordinate axes represent transmissivities. Both of the graphs show thedistributions of the respective emitted lights of the R, G and B. In theresult after adding the microprism, which is shown in FIG. 6( b), it canbe confirmed that centers of the light intensities of the respectivecolors are corrected to the vicinity of the frontal direction and areoverlapped with one another. The color reproductivity in the frontaldirection is 48% at the NTSC rate (57% when designed), which is ameasurement result exceeding the color reproductivity of the direct viewliquid crystal display device added with the conventional 13.3-inchcolor filter (42% when designed). In this embodiment, a light diffusingmember is not used concurrently, and the angle correction effect isbrought only from the microprism. Accordingly, a range of a viewingangle at which the chromaticity is uniform falls within a relativelynarrow value range from −9 degrees to +12 degrees. However, byconcurrently using the diffusion film having appropriate diffusionpower, the viewing angle can be extended to a wide range fromapproximately −20 degrees to +20 degrees under such a condition wherethe frontal luminance is set at approximately 60%. It is demonstratedthat, by adopting the liquid crystal cell 20 in this embodiment in sucha way, the viewing angle at which a color reproduction range and colorbalance are kept uniform is enhanced as compared with the case of usingthe existing optical film for the purpose of correcting the viewingangle.

Next, the black matrix (BM) 25 to which this embodiment is applied willbe described. In the liquid crystal display device to which thisembodiment is applied, as the light source 11, for example, a triodefluorescent tube that is a white light source is used. In this triodefluorescent tube, besides spectrum components of the wavelengths of thered (R), green (G) and blue (B), for example, spectrum componentsincluding small peaks in wavelengths of orange and cyan are present. Ithas conventionally been a problem that these spectrum componentsessentially deteriorate the color reproductivity of the liquid crystaldisplay device. Accordingly, in this embodiment, the pixels of theliquid crystal cell 20 and the black matrix 25 in the liquid crystalcell 20 are redesigned, and a configuration is made such that thewavelength component of the orange or cyan, which hinders the colorreproductivity of the pixels, is cut off. Moreover, in addition to this,the microprism structure different in shape for each sub-pixel is formedaccurately, thus the color reproductivity in the color filterless liquidcrystal display device is enhanced.

FIGS. 7( a) and 7(b) are graphs, each showing a relationship between aposition of the black matrix 25 and a light source spectrum. FIG. 7( a)shows a relationship in the case of adopting a conventional black matrixof an equal interval, and FIG. 7( b) shows a relationship between theposition of the black matrix 25 adopted in this embodiment and the lightsource spectrum. Each abscissa axis represents a pixel position (μm),and each ordinate axis represents an incident light spectrum in theliquid crystal cell 20. As shown in FIG. 7( a), in the case of applyingthe liquid crystal cell pixels and black matrix of the equal interval tothe color filterless liquid crystal display device, for example, thewavelength component of the orange that hinders the color reproductivitycannot be sufficiently cut off, or the wavelength component of the cyancannot be cut off completely, either. However, in FIG. 7( b), width ofeach sub-pixel of the liquid crystal cell 20 and width of the blackmatrix 25 are changed, and optimization design is implemented therefor,thus sufficiently cutting off the wavelength component of the orange andthe wavelength component of the cyan. Specifically, in order tosufficiently cut off the orange wavelength component, the width of theblack matrix 25 present between the sub-pixels of the green (G) and red(R) in each pixel is reduced by, for example, 5 μm on the green (G)sub-pixel side, and meanwhile, the width is increased by, for example,20 μm on the red (R) sub-pixel side. Moreover, in order to sufficientlycut off the cyan wavelength component, the width of the black matrix 25present between the sub-pixels of the blue (B) and green (G) in eachpixel is increased by, for example, 10 μm on the green (G) sub-pixelside. In such a way, the pixel widths of the liquid crystal cell 20 andthe pixel widths of the black matrix 25 are adjusted, thus making itpossible to increase the color reproductivity to approximately 1.15 to1.2 times that in the case shown in FIG. 7( a) before applying such awidth change.

Embodiment 2

Next, as Embodiment 2, an example using a microlens structure will bedescribed. Note that, for similar functions to those in Embodiment 1described for the microprism structure, the same reference numerals willbe used, and here, detailed description thereof will be omitted.

In the conventional color filterless liquid crystal projection device,because of the viewing angle dependencies different for each color andthe angle expansion by the condensing function element, a diffusioneffect occurs in a process from the liquid crystal cell 20 to aprojecting optical element, thus causing a problem of lowering the colorreproductivity/resolution, which is caused by color mixture and blur. Inorder to solve this and to obtain a display image excellent in colorreproductivity and clear without blur, a method of correcting in anglethe light of every wavelength, which is emitted from the liquid crystalcell, into a substantially parallel light mainly directed to the frontaldirection, and making the light incident onto the projecting opticalelement such as a projection lens is the most effective. For this, amicrolens structure, in which two kinds of polymers are used and tiltangles are set respectively in response to incident angles differentdepending on the wavelengths of the incident components for eachsub-pixel, is formed in the liquid crystal cell 20. In such a way, thesubstantially parallel light mainly directed to the frontal directioncan be obtained from all of the sub-pixels. The substantially parallellight mentioned here indicates a luminous flux emitted in an aligningmanner to a range of ±10 degrees or less, and desirably ±5 degrees orless, with respect to the frontal direction.

FIGS. 8 and 9 are views, each showing an example of mounting thismicrolens on the liquid crystal cell 20. For example, for optical designcondensing a light in the vicinities of the liquid crystal layer andblack matrix, structures in FIGS. 8 and 9 are determined in response topositional relationships between the black matrix 25 and microlensstructure portions 50 and 60. In this embodiment, the angle correctionand substantial light paralleling are performed while corresponding indetail to an incident distribution to each sub-pixel, and performance inluminance/chromaticity is enhanced. Besides the color filterless liquidcrystal projection device, this structure can also be applied to thecolor filterless and direct view liquid crystal display device shown inFIG. 1, and a similar effect can be obtained there.

In each of FIGS. 8 and 9, two kinds of polymers in which the sub-pixelcycle is 88 μm and refractive indices are 1.55 and 1.408 are combined,and each of the microlens structure portions 50 and 60 is formed. InFIG. 8, for the microlens structure portion 50, a high refractive indexlayer 51 is provided on an incident side (bottom side), and a lowrefractive index layer 52 is provided on an emitting side (top side). Amicrolens for each sub-pixel, which is formed of these high refractiveindex layer 51 and low refractive index layer 52, is formed to protrudedownward (to swell from the low refractive index layer 52-side).Meanwhile, in FIG. 9, for the microlens structure portion 60, similarly,a high refractive index layer 61 is provided on an incident side (bottomside), and a low refractive index layer 62 is provided on an emittingside (top side). A microlens for each sub-pixel, which is formed ofthese high refractive index layer 61 and low refractive index layer 62,is formed to protrude upward (to swell from the high refractive indexlayer 61-side). Moreover, in each of FIGS. 8 and 9, as the cylindricallens array 16 shown in FIG. 1, a condensing lens 16-1 arranged over thewhole of one pixel (three sub-pixels) is illustrated.

Moreover, in these FIGS. 8 and 9, in order to obtain the substantiallyparallel light mainly directed to the frontal direction from all of thesub-pixels, these microlens structure portions 50 and 60 are formed in astate of being given predetermined tilt angles. There was obtained aresult to the effect that the viewing angle characteristics and thecolor reproductivity in the frontal direction cover the widest rangewhen the tilt angles implemented for the microlenses of the respectivesub-pixels become 45 degrees (for the red and blue sub-pixels) and 14degrees (for the green sub-pixel). If the tilt angles implemented forthe microlenses for each sub-pixel are set as described above,thicknesses of the microlens structure portions 50 and 60 become thick,exceeding 10 μm. For example, the thickness becomes approximately 80 to100 μm in some cases.

In this case, the optimum curvature radius R2′ when the refractiveindices of the low refractive index layers 52 and 62 are 1 for curvatureR1 of the condensing lenses 16-1 shown in the lowermost portions ofFIGS. 8 and 9 is used. The curvature radius R2′ is represented as:R2′=(⅓)R1 Then, curvature radius R2 of the microlens in the liquidcrystal cell 20 is calculated from the following relationship:R2=R2′(nH−nL)/(nH−1) where nH and nL are an absolute refractive index ofthe high refractive index layers 51 and 61 and an absolute refractiveindex of the low refractive index layers 52 and 62, both of which formthe microlens structure portions 50 and 60 in the liquid crystal cell20. Note that giving the tilt angles to the microlenses formed in therespective sub-pixels in the liquid crystal cell 20 in each of FIGS. 8and 9 has the same meaning as in that both microlenses of the red andblue sub-pixels are translated parallel to the green sub-pixel side.Parallel translations of the microlenses for giving desired tilt anglesare easily calculated by use of the cycle of the sub-pixels and thecurvatures of the microlenses as parameters.

FIGS. 10 and 11 are views, each showing an example of mounting theFresnel-type microlens shape on the liquid crystal cell 20. Similarly tothe above-mentioned microprism shape, the thinned Fresnel-type microlensshape can also be adopted. The two-layer flat structure of the thinnedFresnel-type microlens shape is adopted, thus making it possible tomaintain the evenness of the cell gap and to simplify the manufacturingprocess. In order to obtain this Fresnel-type microlens shape, two kindsof polymers are used in the liquid crystal cell 20, and a Fresnel-typemicrolens shape having shapes corresponding to different tilt angles isformed in response to incident angles different depending on thewavelengths of the incident components for each sub-pixel. Concretely,only asymmetry corresponding to the tilt angles is given, andaccordingly, it is made possible to thin the shape. In this case also,the substantially parallel light mainly directed to the frontaldirection can be obtained from all of the sub-pixels.

Here, similarly to FIGS. 8 and 9, two kinds of polymers in which thecycle of the sub-pixels is 88 μm and the refractive indices are 1.55 and1.408 are combined, and Fresnel-type microlens structure portions 70 and80 are formed. In FIG. 10, for the Fresnel-type microlens structureportion 70, a high refractive index layer 71 is provided on an incidentside (bottom side), and a low refractive index layer 72 is provided onan emitting side (top side). A Fresnel-type microlens for eachsub-pixel, which is formed of these high refractive index layer 71 andlow refractive index layer 72, is formed to protrude downward (to swellfrom the low refractive index layer 72-side). Meanwhile, in FIG. 11, forthe Fresnel-type microlens structure portion 80, similarly, a highrefractive index layer 81 is provided on an incident side (bottom side),and a low refractive index layer 82 is provided on an emitting side (topside). A Fresnel-type microlens for each sub-pixel, which is formed ofthese high refractive index layer 81 and low refractive index layer 82,is formed to protrude upward (to swell from the high refractive indexlayer 81-side). Due to optical design in which a light is condensed inthe vicinities of the liquid crystal layer 23 and the black matrix 25,which are shown in the drawings, it is desirable to appropriately selectthe structures in FIGS. 10 and 11 in response to positionalrelationships between the black matrix 25 and the Fresnel-type microlensstructure portions 70 and 80. The angle correction and the substantiallight paralleling are performed while corresponding in detail to anincident distribution to each sub-pixel, and performance inluminance/chromaticity is enhanced. Besides the color filterless liquidcrystal projection device, these structures can also be applied to thecolor filterless and direct view liquid crystal display device, and asimilar effect can be obtained there.

Note that, as another embodiment, it is also possible to form adiffraction grating structure in the liquid crystal cell 20.Specifically, a diffraction grating structure of a triangularcross-sectional shape is formed in the liquid crystal cell 20 by use oftwo kinds of polymers. Similarly to the Fresnel-type microprismstructure described with reference to FIG. 3, a diffraction grating withcycles different depending on the wavelengths of the incident componentsfor each sub-pixel is formed, and an emission distribution includingdiffraction components mainly directed to the frontal direction isobtained from all of the sub-pixels. Furthermore, in the microprism ordiffraction grating built in the liquid crystal cell 20, a shape thereofis changed into a shape in which variations are added to the cyclicstructure depending on positions in the respective sub-pixels. Thus, afine adjustment for the angle correction and the diffusion function canbe performed in response to the spectrum distributions of theintensities of the incident light onto the respective sub-pixels, andperformance enhancements in the luminance, the chromaticity and theviewing angle can be achieved.

Next, a method of manufacturing the microprism/microlens built in theliquid crystal cell 20 will be described.

FIG. 12 is a flowchart showing a process of the method of manufacturingthe microprism/microlens. First, based on design values, a lens shapeand the like are cut on a surface of a metal die material, and thus ametal die is fabricated (Step 101). As a die material, metal such as Cu,Al and Ni may be used, or silicon elastomer and the like may be used.After cleaning this fabricated metal die (Step 102), low refractiveindex photo-setting resin, for example, fluororesin is coated thereon(Step 103). Meanwhile, after cleaning the glass substrate 22 (Step 121),a surface treatment for enhancing adhesiveness to the resin isimplemented for a surface of the glass substrate 22 (Step 122). In Step104, the metal die on which the resin is coated in Step 103 and theglass substrate 22 for which the surface treatment is implemented inStep 122 are pasted together (Step 104), and are irradiated with anultraviolet ray to set the low refractive index resin (Step 105). Next,the glass substrate 22 to which the resin is adhered is peeled off fromthe metal die (Step 106), and thus the fabrication of themicroprism/microlens is completed. Furthermore, in this embodiment, onthe glass substrate 22 on which the microprism/microlens structure isformed of the low refractive index resin, high refractive indexphoto-setting resin, for example, acrylic resin is coated (Step 107).Then, a planarizing die which is prepared separately and cleaned in Step111 is pasted on the resultant, and again, an ultraviolet ray isirradiated thereon, and the resin is set (Step 108). The planarizing dieis not limited to the metal. Finally, the planarizing die is peeled offfrom the glass substrate 22 on which the planarized microprism/microlensstructure formed of the two kinds of resins is formed (Step 109). Thus,the manufacture of the microprism/microlens is ended (Step 110).Thereafter, a creation process of the liquid crystal cell 20 isexecuted.

The manufactured microprism/microlens is pasted to each sub-pixel in theliquid crystal cell 20 in a state of meeting high accuracy required. Forthis position alignment, a positioning method using an “alignment mark”is utilized. For example, by use of ultraviolet-setting resin and ametal die, the “alignment mark” made of a cross mark having a width of150 μm is formed on the metal die. Then, resin is coated on this metaldie, and further, the metal die is aligned with the glass substrate 22having an “alignment mark” similar to that of the metal die by use of ahigh-resolution camera, and the resin is set by an ultraviolet ray. Insuch a way, for example, position alignment is realized at accuracy of±15 μm or less per 200 mm.

As described in detail, according to the respective embodiments, in thecolor liquid crystal display device in which the incident angles andwavelengths of the light made incident onto the sub-pixels correspondingto the respective colors of the R (red), G (green) and B (blue) aredifferent for each sub-pixel, the microprism structure or the likeoptimized for each sub-pixel corresponding to each color is introduced.Thus, the emission angles of the light of the respective colors of R, Gand B from the liquid crystal cell 20 can be corrected to the emittinglight distribution similarly symmetric with respect to the frontaldirection as a center. Moreover, the microlens structure optimized foreach sub-pixel corresponding to each color is introduced, thus making itpossible to substantially parallel the emission angles of the light ofthe respective colors R, G B from the liquid crystal cell 20 whiledirecting the light to, for example, the frontal direction. Furthermore,another optical function element, for example, an element having a lightdiffusion function or the like is interposed in the liquid crystal cell20, thus making it possible to provide a display device realizing adisplay image having a wide-range color reproductivity, a wide viewingangle, and clearness without blur.

The color filterless liquid crystal display device is a techniquepotentially having high color reproductivity (at the NTSC rate) becausethe device takes in the wavelength component suitable for the sub-pixelcorresponding to each color. The microprism/microlens as mentioned aboveis introduced, and thus, for example, in the case of the direct viewliquid crystal display device, it is possible to enhance the colorreproductivity in the frontal direction, which is important in practicaluse. Moreover, the viewing angle wide and symmetric with respect to thefrontal direction as a center is made possible. In an example of theoptimum prism design value, the color reproductivity in the frontaldirection is 57% at the NTSC rate, covers a range of ±10 degrees evenwithout a scattering function, and the uniform chromaticity is obtained.A light diffusing member in response to a desired viewing angledistribution is combined with this, or an appropriate light diffusingeffect is provided concurrently to the prism itself, thus making itpossible to fabricate a direct view color liquid crystal display devicewhich is high luminance and has a distribution of an emitted light withuniform chromaticity. Moreover, in the liquid crystal projection device,the light can be subjected to the angle correction to the parallel lightarrayed to the frontal direction.

Furthermore, in this embodiment, the prism/microlens structure isintroduced into the liquid crystal cell 20, and thus the liquid crystaldisplay device without any parallax is provided.

Still further, when the prism/lens shape is transferred from the metaldie to the glass substrate for the liquid crystal cell, not a heatingprocess but the light irradiation process is used, and thus themicroprism/microlens structure without causing any tolerance from thedesign value due to thermal expansion can also be provided.

As an example of making full use of the present invention, besides thecolor filterless and direct view liquid crystal display device, a colordisplay device such as a color filterless liquid crystal projectiondevice, and an optical element for use in these image display devicesare given.

Although advantageous embodiments of the present invention have beendescribed in detail, it should be understood that various changes,substitutions and alternations can be made therein without departingfrom spirit and scope of the inventions as defined by the appendedclaims.

What is claimed is:
 1. A method of forming an optical element for acolor display device, the method comprising: forming a lens shaped diefrom a first die material; coating a low refractive index photo-settingresin on the lens shaped die; pasting the lens shaped die to asubstrate; irradiating the coated low refractive index photo-settingresin so as to set the low refractive index resin on a surface of thesubstrate and form a low refractive index layer; removing the lensshaped die from the low refractive index layer set on the substrate;coating a high refractive index photo-setting resin on the lowrefractive index layer by use of a planarizing die; irradiating thecoated high refractive index photo-setting resin so as to set the highrefractive index resin and form a high refractive index layer; andremoving the planarizing die from the high refractive index layer set onthe low refractive index layer.
 2. The method of claim 1, wherein thehigh refractive index layer and the low refractive index layer havedifferent shapes for each of sub-pixels corresponding to respectivecolors of red (R), green (G) and blue (B), and wherein an uppermostportion of the high refractive index layer for each of the R, G and Bsub-pixels has a curved shape.
 3. The method of claim 2, wherein thehigh refractive index layer and the low refractive index layer form aprism structure, and angles of prisms differ for each of the sub-pixels.4. The method of claim 2, wherein the high refractive index layer andthe low refractive index layer form a lens structure for each of thesub-pixels.
 5. The method of claim 1, wherein the first die materialcomprises one of: a metal material and a silicon elastomer material. 6.The method of claim 5, wherein the first die material comprises one of:copper, aluminum, and nickel.
 7. The method of claim 1, wherein thesubstrate comprises glass.
 8. The method of claim 7, further comprisingsurface treating the glass substrate prior pasting the low refractiveindex coated lens shaped die thereto, so as to enhance adhesiveness ofthe low refractive index resin to the glass substrate.
 9. The method ofclaim 2, wherein the high refractive index layer has a refractive indexof about 1.55.
 10. The method of claim 2, wherein the low refractiveindex layer has a refractive index of about 1.408.